Yes the Schrader valves come out replace both high and low side.
Your leak could be were the orifice tube is installed or at the condenser were it hooks up most leaks are at these two points and hard to spot. One other spot on older models is at the A/C Receiver Drier/Accumulator were it snaps into the firewall/Evaporator that spot works lose and is hard to see.
Evaporators usually don't get leaks I would look at all other spots first were they snap into the Drier/Accumulator yes.
Last edited by 98DAKAZ; 07-21-2014 at 12:15 AM.